The Government's plan to restrict the teaching profession to graduates with a 2:2 or above "doesn't make sense", a leading private school headmaster has warned.
Richard Cairns, head of prestigious Brighton College, said a better indicator of how good a teacher would perform was A-level results.
He went on to claim that the Government's decision to restrict teacher training to those with a second-class degree is wrong since almost everyone receives one and the quality of universities is so varied.
Mr Cairns, who employs Oxford and Imperial College graduates with third- class degrees, said A-level results were a better measure of teacher quality than degree class because they were part of a national exam.
"I wouldn't appoint someone with only a C-grade in English," he said. "The fact they have a 2:2 in media from Portsmouth University wouldn't come into it.
"The Government is doing the right thing but in the wrong way. The quality of teachers is the single most important factor for improving education, but the insistence on a 2:2 just doesn't make sense.
"The Government should look at performance in the sixth-form; A-levels are a much easier measure for an employer. We all know that the quality of a 2:2 varies in different universities and different subjects. The university system is in a mess."
He said that in Finland, which consistently performs highly in international pupil tests, the state puts emphasis on recruiting high- quality teachers, looking closely at high school certificates to pick out the best candidates for training.
Mr Cairns' comments come just months after research from Buckingham University revealed that 61 per cent of entrants to undergraduate BEd teacher training courses have the equivalent of two A-levels, falling to 48 per cent of those who specialised in science and 53 per cent in maths.
About 91 per cent of graduates going into teacher training have a second- class degree or above.
Experts have warned that restricting teacher training to certain degrees will cause teacher shortages in already hard-pressed subjects such as science.
Union leaders have also claimed that high academic performance doesn't always equal good teaching. New psychometric tests to assess a candidates' suitability for teaching will be introduced in 2012 for all those hoping to enter teacher training.
Mr Cairns spoke out prior to the annual conference of the 100 Group of leading state and independent school headteachers taking place in London this week.
Other speakers at the conference will include the Finnish ambassador to England, Pekka Huhtaniemi, who will give a presentation on how other countries can learn from his country's educational success.
Mr Huhtaniemi told The TES that although his country's enviable Pisa results were an asset for promoting the country in the world, they were not "getting carried away with them".
In the most recent set of Pisa results announced last December, Finland lost its literacy top spot to Shanghai. It was placed third behind South Korea.
91% - Graduates going into teacher training who have a 2:2 or above
100 GROUP CONFERENCE - `We've assumed our way is best'
Heads attending the 100 Group conference will discuss whether British education is falling behind that of other countries, following disappointing rankings in the Pisa international tests in reading, maths and science.
Mr Cairns told The TES that, until very recently, British educationalists had been "myopic", with conferences that focused on swapping good practice between schools within the country.
"We've been arrogant, we've assumed that our way of doing things is right," he said.
International testing, he added, although flawed, indicated that Britain was falling behind and could learn from top-performing parts of the world such as Shanghai in China.
He said that high-ranking Asian countries could teach us about discipline, work ethics and the advantages of a longer school day, and that countries such as Germany had much to offer in terms of vocational education.
He added that the UK needed to be open to foreign influences. "Schools can be very conservative places and there are so many establishment figures who object to change, including in the independent sector," he said.
- Original headline: A-levels, not degrees, are what count in teacher recruitment, says top head